Organic electronic devices that emit light, such as light-emitting diodes that make up displays, are present in many different kinds of electronic equipment. In all such devices, an organic active layer is sandwiched between two electrical contact layers. At least one of the electrical contact layers is light-transmitting so that light can pass through the electrical contact layer. The organic active layer emits light through the light-transmitting electrical contact layer upon application of electricity across the electrical contact layers.
It is well known to use organic electroluminescent compounds as the active component in light-emitting diodes. Simple organic molecules such as anthracene, thiadiazole derivatives, and coumarin derivatives are known to show electroluminescence. Such polycyclic aromatic compounds due to their rigid structures possess attractive properties such as high thermostability (e.g., melting points are often above 400° C.) and good stability to photo-oxidation, which lead to LED devices with longer lifetimes.
However, there is a continuing need for electroluminescent compounds.